1. Field of the Invention
This invention relates to a solar cell module, particularly relates to a solar cell module capable of outputting a high voltage.
2. Description of Prior Art
A solar power generation system using a solar cell, which does not give harmful effect to the environment, has become popular as a domestic power system.
Crystalline semiconductor material such as single crystalline silicon and polycrystalline silicon, amorphous semiconductor material such as amorphous silicon and amorphous silicon germanium, and compound semiconductor material such as GaAs and CdTe or the like have been used for composing a solar cell. Particularly, a solar cell using amorphous semiconductor material is free from restrictions on selection of a substrate and output design, and can be manufactured at a low cost.
FIG. 1 is a cross-sectional view illustrating a structure of a conventional solar cell module using an amorphous semiconductor.
As shown in FIG. 1, the conventional solar cell module using an amorphous semiconductor includes a plurality of photovoltaic elements 2 mounted on a substrate 1 formed with translucent and insulative material such as glass and plastic. The plurality of photovoltaic elements 2 are cascade-connected with each other and output predetermined electric power. The photovoltaic element 2 comprises a first electrode 11 of conductive translucent material such as tin oxide (SnO2), indium tin oxide (ITO), and zinc oxide (ZnO), a photovoltaic conversion layer 12 of amorphous semiconductor having pin junction inside, and a second electrode 13 of highly reflective material such as Ag and Al or the like laminated in this order. The second electrode 13 is buried in a separating part between the adjacent photovoltaic conversion layers 12 and is contact with the first electrode 11 so that the adjacent photovoltaic elements 2 are electrically connected in series with each other.
A protective layer 3 covers a surface of the photovoltaic elements 2 for preventing a scratch or the like on the surface of the photovoltaic element 2 in the later process. The protective layer 3 is generally formed with epoxy resin. A rear surface member 4 of glass, plastic, steel or the like is adhered on the rear surface of the photovoltaic element 2 through an adhesive layer 5 of thermal plastic resin such as EVA (ethylene vinyl acetate) or the like. The adhesive layer 5 is formed with water-repellent material and prevents moisture from penetrating.
Electromotive force generated by the photovoltaic element 2 is taken out to the external through a lead wire (not shown) from the first and second electrodes of the photovoltaic element 2 arranged on both ends.
FIG. 2 is a schematic view illustrating a general structure of a domestic solar cell system using the above mentioned solar cell module. In FIG. 2, a plurality of solar cell modules 201 are arranged on a roof of a house and direct output from the plurality of the solar cell modules 201 is accumulated and is introduced into a connection box 202. The direct output from the connection box 202 is converted into alternating output by an inverter 203, and is supplied to a load in a house 205 through a distribution board 204. When power supplied from the solar cell modules 201 runs short at night, electric power can be supplied to the load in a house 205 from the commercial power system 206.
Alternating output from the inverter 203 is adjusted to be 100V because the load in a house 205 is for 100V. When considering about a loss in the inverter 203 and a lowered output from the solar cell modules 201 caused by cloud weather, an operating voltage of the solar cell modules 201 which is input to the inverter 203 is preferably about 200V in order to make alternating output of the inverter 203 100V.
Generally an operating voltage per single solar cell module using single crystalline silicon is approximately 50V. When four or five solar cell modules are connected in series and form a group, the operating voltage of approximately 200V is output from the group of solar cell modules and is input to the inverter 203.
A solar cell module using amorphous semiconductor which is free from a restriction on output designs and outputs a higher voltage has been proposed. (JP, 6-60155, U)
A structure of the solar cell module is explained by referring to FIGS. 3-5. FIG. 3 is a plan view of the solar cell module; FIG. 4 is a cross-sectional view along Axe2x80x94A line of FIG. 3; FIG. 5 is a cross-sectional view along the Bxe2x80x94B line of FIG. 3. Elements having the same functions have the same numeral references indicated in FIG. 1.
The photovoltaic element 2 is formed on the substrate 1 which is formed with translucent material such as glass and plastic or the like and has an insulating surface. The photovoltaic element 2 comprises a first electrode 11 of translucent material such as SnO2, ITO, or ZnO, a photovoltaic conversion layer 12 of amorphous semiconductor having pin junction, and a second electrode 13 of highly reflective metal material such as Ag and Al or the like laminated in this order.
A first electrode separating part 21 formed by exposing the insulating surface of the substrate 1 separates the adjacent first electrodes 11. A photovoltaic conversion layer separating part 22 formed by exposing a surface of the first electrode 11 separates the adjacent photovoltaic conversion layers 12. A second electrode separating part 23 formed by exposing a surface of the photovoltaic conversion layer 12 separates the adjacent second electrodes 13. The second electrode 13 is buried in the photovoltaic conversion layer separating part 22 so as to make contact with the first electrode 11, thus the adjacent photovoltaic elements 2, 2 are electrically connected in series with each other.
The solar cell module, as shown in FIG. 3, includes a first group of integrated elements 30 comprising a plurality of photovoltaic elements 2 electrically connected in series with each other, and a second group of integrated elements 40 comprising a plurality of photovoltaic elements 2 electrically connected in series with each other. A groove 8 is formed around the first and second groups of integrated elements 30, 40, for preventing leak through the first electrode, the photovoltaic conversion layer, and the second electrode attached to a side surface of the substrate 1 when forming them. The groove 8 is formed by removing the first electrode 11, the photovoltaic conversion layer 12, and the second electrode 13, and exposing the insulating surface of the substrate 1.
The first group of integrated elements 30 and the second group of integrated elements 40 are arranged in parallel by interposing a separating part 50. The separating part 50 is formed by removing the first electrode 11, the photovoltaic conversion layer 12, and the second electrode 13, and exposing the insulating surface of the substrate 1 so that the separating part 50 electrically separates the first group of integrated elements 30 and the second group of integrated elements 40. Directions of series connections in the first group of integrated elements 30 and the second group of integrated elements 40 are opposite in FIG. 3. In the first group of integrated elements 30, the negative is on the right side of the figure and the positive is on the left side of the figure. In the second group of integrated elements 40, the negative is on the left side, and the positive is on the right side.
The first and second groups of integrated elements 30, 40 are electrically connected in series by a connecting wire 6. Electric output is taken out to the external from a pair of positive and negative output terminals 7 arranged on one side of the substrate 1. The connecting wire 6 is formed with, for example, solder plating copper foil. The connecting wire 6 is connected to the first electrode 11a positioned on the left end of the first group of integrated elements 30 and the second electrode 13a on the left side of the second group of integrated elements 40 by solder. An output terminal 7 on the positive side is connected to the first electrode 11b on the right end of the second group of integrated elements 40 and an output terminal 7 on the negative side is connected to the second electrode 13b on the right end of the first group of integrated elements 30 through the lead wire (not shown).
In the above structure, because the two groups of integrated elements 30 and 40 are provided, a higher voltage can be output in comparison with a single group of integrated elements. For example, an operating voltage by one photovoltaic element using amorphous silicon is about 0.6V, and a group of integrated elements formed of one hundred of the photovoltaic elements connected in series can generate output voltage of about 60V.
When two groups of the integrated elements are provided, output voltage of about 120V can be obtained. When the photovoltaic element has a lamination structure having a plurality of pin junctions, operating voltage per single photovoltaic element can increase up to about 2V, and thus the total operating voltage reaches as high as about 200V.
However, when the protective layer 3, the adhesive layer 5, and the rear surface member 4 are provided on a rear surface of the photovoltaic element 2 as shown in FIG. 1, the solar cell module capable of outputting a high voltage does not demonstrate high reliability.
As described above, when a high voltage is accumulated by a single group of integrated elements, a high electric field is applied between the groups of the integrated elements 30, 40. Therefore, when moisture or the like penetrates from a slit or the like into the separating part 50 for separating the groups of integrated elements 30, 40, short circuit occurs, resulting in a great degradation of cell characteristics. Particularly, in the separating part 50 applied high electric field, a generated electric field is far greater than between photovoltaic conversion elements of a conventional solar cell module, and penetration of even a little of moisture can not be ignored.
This invention was made to solve the above problems and has an objective to provided a reliable solar cell module capable of outputting a high voltage.
A solar cell module of this invention comprises a substrate having an insulating surface, a group of integrated elements including a plurality of photovoltaic elements electrically connected in series on the substrate, a separating part for electrically separating the plurality of the groups of integrated elements arranged in parallel on the substrate, a connecting member for electrically connecting the plurality of the groups of integrated elements in series with each other, rear surface member provided on rear surface sides of the plurality of the groups of integrated elements, and an adhesive layer containing resin for adhering the rear surface member on the rear surface side of the plurality of the groups of integrated elements. The adhesive layer is provided so as to cover the rear surface of the group of integrated elements except for an area corresponding to the separating part.
When adhering the rear surface member on the rear surface of the group of integrated elements by interposing the adhesive layer, the adhesive layer is provided on the rear surface of the group of integrated elements except for the separating part. Therefore, if moisture penetrates into the adhesive layer, leak current between the group of integrated elements through the moisture can be prevented. Thus, a reliable solar cell module capable of outputting a high voltage can be provided.
A groove is formed on the substrate by exposing the insulating surface of the substrate so as to surround the plurality of the groups of integrated elements.
The adhesive layer is formed so as to cover the rear surface of the group of integrated elements except for an area corresponding to the groove.
In the above structure, a groove surrounding the group of integrated elements prevents leak current through the photovoltaic element attached on the side surface of the substrate. When the adhesive layer corresponding to the groove is removed, leak current through moisture can be prevented even when the moisture penetrates in the adhesive layer.
The photovoltaic element comprises an amorphous semiconductor.
A protective layer containing resin is formed on a whole rear surface of the plurality of the groups of integrated elements including the separating part.
A moisture proof member is provided on the protective layer positioned on the separating part.
A moisture proof member is provided on the separating part and the protective layer is provided thereon.
Weatherable insulating member provided on the separating part can protect the separating part which is likely to be short-circuited electrically.
The connecting member comprises a lead wire, and an insulating film is formed between the lead wire and the rear surface of the plurality of the groups of integrated elements.
The insulating film between the rear surface member 4 comprising a metal plate and an output lead can secure the insulation of the rear surface member. Therefore, the insulation with the rear surface member can be secured when using the integrated solar cell panel 1a for outputting high voltage.
A solar cell module comprises a substrate having an insulating surface, a group of integrated elements including a plurality of photovoltaic elements electrically connected in series on the substrate, a separating part for electrically separating the plurality of the groups of integrated elements arranged in parallel on the substrate, a connecting member for electrically connecting the plurality of the groups of integrated elements in series with each other, rear surface member provided on rear surface sides of the plurality of the groups of integrated elements, and an adhesive layer containing resin for adhering the rear surface member on the rear surface side of the plurality of the groups of integrated elements. A width of the separating part located between the adjacent groups of integrated elements is determined depending on a potential difference generated between the adjacent integrated elements which sandwich the separating part.
The separating part is formed by exposing the insulating surface of the substrate.
A width of the separating part satisfies the relational expression D(xcexcm)xe2x89xa73xc3x97V(V) when letting the potential difference be V.
Leak current generated through the separating part can be suppressed by determining a width of the separating part by a potential difference between the photovoltaic elements which are arranged oppositely and interpose the separating part.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when collected conjunction with the accompanying drawings.